After Meat, Mustard

In Latin, “Post bellum, auxilium.” We have also, “After death,
the doctor,” which is the German, “Wann der kranke ist todt, so kommt
der arztnei” (when the patient's dead, comes the physic). To the same
effect is “When the steed is stolen, lock the stable door.” Meaning,
doing a thing, or offering service when it is too late, or when there
is no longer need thereof.